Using K2CO3 - Fertilizing - Aquatic Plant Central

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Old 07-30-2005, 04:10 PM   #1 (permalink)
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Default Using K2CO3

I acquired some K2CO3 today to use for increasing the kH of my water. I am not very good at chemistry, yet, so I wonder if someone coul dhelp me figure out a solution to dose to my tanks. Say x grams in 500ml H20 to raise the kH of 10 gallons of water.

Any help would be most appreciated and I would especially love it if someone could show the calculations so I understand how to do it in the future

This also might be a good thing to add to the Fertilator if someone wanted to do the math for APC.
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Old 07-30-2005, 06:11 PM   #2 (permalink)
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Where'd you get that stuff?
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Old 07-30-2005, 07:48 PM   #3 (permalink)
 
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I do not think that is a long-term solution for increasing KH. As the plants consume the K, they release H+ ions, which will react with the CO3-2 ion to CO2 and H2O.

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Frank
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Old 07-30-2005, 08:25 PM   #4 (permalink)
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Phil, I got it from a friend

Frank, thank you for your input. What you say certainly seems to make sense but I view this as a temporary solution at best. Basically for 2-3 of the summer months, my town changes to a different water supply that has no kH. I plan to add back the kH as needed with each water change, basing the dose by testing sometime after the wc. How does adding potassium carbonate differ from using baking soda or even calcium carbonate? Admitidly though the plants probably use less Ca or Na than K but still, I do not like adding Na (no matter what some might say about it) and my Gh of 11 tells me I probably don't need any more Ca. I also have been wondering lately if I'm not running a bit low on K, although I have nothing to back up that other than a feeling.....

The K2CO3 is 99.5% pure, BTW if that helps with the math at all.
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Old 07-30-2005, 09:09 PM   #5 (permalink)
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I think I might have figured it out on my own but need someone to double check it for me....

Apparently the equation to find grams of dry compound to use to get a specific concentration of a chamical can be found here I did the math to find the mass percentage factor for K2CO3 (equation found here and plugged it into the first formula. The conversion for degrees hardness to ppm is 17 ppm for 1 degree. This gives me...

17x3.77x10/[.60x1000]=1.068

So 1.07 grams of K2CO3 will raise 10gallons of water by 1 degree kH. Did I do that right?


If so, then if I want to raise my tank water by 3 degrees kH I need to add 3.21grams, correct?

am I doing the math correct in that the dosing will add 66ppm of K?
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Old 07-31-2005, 08:08 AM   #6 (permalink)
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Well I double checked this and found I did the mass percentage factor part wrong..... here is the corrected figuring:

So I just googled and found this calculator.... http://chemmac1.usc.edu/bruno/java/compo.html

it tells me

K- 56.58
C- 8.69
O- 34.73

Then I should add C+O= 43.41%

Move the decimal 2 to the left:
K- .567
CO3- .434

then I should use this equation:
Grams of compound to use to get a specific concentration in ppm:

[target ppm x 3.77(gallon to liter conversion) x actual aquarium gallons] / [mass percentage factor of element x 1000] = dry grams needed

so:
there are 17 ppm per 1 degree hardness

(17 x 3.77 x 10)/[.436 x 1000]
640.9 / 436
=1.47 grams of K2CO3 will raise 10 gallon H2O 1 degree

Now to figure the K added by this I use this equation:

To go from the actual grams of a material added to the tank, to the resulting ppm, use this equation:
[(grams of compound added) x (mass percentage factor) x (1000)] / [3.77 x (actual gallons)] = (resulting ppm)


so:

[1.47 x .567 x 1000] / [3.77 x 10]
833.49 / 37.7
22.1 ppm K


If I raise my kH 3 degrees i will be adding 66ppm K

So I figure that dosing KNO3 and KH2PO4 4x week gives ma about 20ppm K, 32ppm NO3, 1.5ppm PO4

thats 86ppm K a week!!! Something tells me that is not a good idea


Did I do my math right and will the extra K be a problem?
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Old 08-01-2005, 04:29 AM   #7 (permalink)
 
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You switched .434 to .436 when calculating grams from mass percentage. Also 17.9ppm = 1dkH. That java element mass percentage calculator is sweet; thanks. For below I'm going using atomic weights from an old chem book, because it makes more sense to me than the ~spituch computation page. I'm also no chem wiz, so this may be wrong

g K2CO3 = target dKH * (17.9mg CO3/L)/dKH * tank gallons * 3.77L/gal * 138.2mg K2CO3/60.1mg CO3 * 1g/1000mg

This gives ~1.55g to raise 10gal 1dKH.

Simplified for the fertilator if you want:

g K2CO3 = target dKH * tank gallons * .1552g K2CO3/(dKH*gal)

Last edited by czado; 08-01-2005 at 04:32 AM..
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